System For Laser-Based Digital Marking Of Objects With Images Or Digital Image Projection With The Laser Beam Shaped And Amplified To Have Uniform Irradiance Distribution Over the Beam Cross-Section

Abstract

A laser marking system including a laser apparatus to supply a laser beam having a non-Gaussian irradiance distribution over a beam cross-section, the non-Gaussian irradiance distribution of the laser beam has a substantially uniform irradiance distribution over the beam cross-section, a spatial light modulator coupled to receive the laser beam, the spatial light modulator is controlled to generate an output laser beam including an optical pattern across the beam cross-section to mark a target object with the data code matrix, and an optical amplifier coupled to the spatial modulator to receive the laser beam output from the spatial light modulator and generate an amplified laser beam containing the same optical pattern as generated by the spatial light modulator, the amplified laser beam from the optical amplifier having a substantially uniform amplification across the cross-section of the beam, the amplified beam maintaining the substantially uniform irradiance distribution over its beam cross-section.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional No. 61 / 372,197 filed Aug. 10, 2011, and is incorporated herein by reference in its entirety. This application also claims priority to and is a Continuation-In-Part of U.S. application Ser. No. 12 / 204,390 filed Sep. 4, 2008 and is incorporated herein by reference in its entirety.FIELD OF THE INVENTION[0002]The present invention is generally related to laser image amplification marking systems, and, more particularly, to a system comprising a laser beam-shaping arrangement to have a spatially uniform irradiance for the initial beam, a Spatial Light Modulator (SLM) and an optical amplifier configured to provide an amplified beam having a spatially uniform irradiance.BACKGROUND OF THE INVENTION[0003]It is known that optical representation of data, such as machine-readable bar codes, logos, etc., can be attached, placed or marked on products by various means, such as industrial ink jet pr...

AI Technical Summary

Benefits of technology

"The present invention is about a laser marking system that uses a laser beam with a uniform irradiance distribution to mark objects. The system includes a laser apparatus that generates a non-Gaussian irradiance distribution over the beam cross-section, a spatial light modulator that controls the output of the laser beam, and an optical amplifier that amplifies the laser beam while maintaining its uniform irradiance distribution. The laser marking system can generate an optical pattern that contains a data code matrix or a logo to mark the target object. The technical effect of this invention is to provide a laser marking system that can accurately and efficiently mark objects with high-quality images."

Problems solved by technology

Although the technology has made advances in terms of speed and performance, placing a 2-D bar matrix code or a high resolution image on the object can be challenging.

However, certain drawbacks can arise during their operation.

However, the overall power cannot be increased indefinitely and is limited by the damage threshold of the SLM.

The system described in the foregoing patent, however, is somewhat impractical since the physical dimensions and the cross-sectional area of available micromirror devices are relatively small (in the order of few square cm).

That is, the irradiance of the incident laser beam cannot be reduced by a factor greater than L. Any further magnification (M>L) would result in part of the beam to miss the device.

Thus, in practice, Applicant believes that the marking system proposed in the foregoing patent would not be effective for applications requiring optical intensities L times higher than the DMD damage threshold.

Also, in applications where large sized marks are required, with mark size being comparable to the size of a DMD / SLM itself, Applicants submits that the beam expansion and contraction mechanism would be useless.

As a result, the irradiance of the laser beam at the target surface would be Gaussian or non-uniform, which could adversely affect the quality of the marks, whether non-ablative or ablative.

For example, in the case of marks based on ablative marking (as may involve a metal foil), the relatively high irradiance at the center of a Gaussian beam, as compared to substantially lower levels at the outer edges of the beam, could result in a melting of the foil at the center of the mark leaving a hole, whereas the irradiance level at the beam edge may not be sufficiently high to ablate the foil metal.

For example, in the case of non-ablative marking (e.g., photo-chemical change of a coating under laser irradiance), the relatively high irradiance at the center of the Gaussian beam might lead to heat conduction to areas on the target that are not designated for marking, and the relatively weak irradiance at the outer edges of the beam may not be conducive to a color change.

If a 2-D data matrix code is marked on a target (ablative or non-ablative) the non-uniform irradiance distribution would ruin the contrast ratio of the code and a code reader would be unable to read it.

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